Lasers and Nuclei (eBook)

Preface 6
Contents 8
List of Contributors 14
Part I Fundamentals and Equipment 16
1 The Nuclear Era of Laser Interactions: New Milestones in the History of Power Compression 17
1.1 History of Power Compression 17
1.2 Conclusions 19
Acknowledgments 19
References 19
2 High-Intensity Laser–Matter Interaction 21
2.1 Lasers Meet Nuclei 21
2.2 The Most Intense Light Fields 22
2.3 Electron Acceleration by Light 25
2.4 Solid State Targets and Ultrashort Hard X-Ray Pulses 32
2.5 Proton and Ion Acceleration 34
2.6 Conclusion 36
References 36
3 Laser-Triggered Nuclear Reactions 38
3.1 Introduction 38
3.2 Laser–Matter Interaction 39
3.3 Review of Laser-Induced Nuclear Reactions 44
3.4 Future Applications 52
References 54
4 POLARIS: An All Diode-Pumped Ultrahigh Peak Power Laser for High Repetition Rates 59
4.1 Introduction 59
4.2 Ytterbium-Doped Fluoride Phosphate Glass as the Laser Active Medium 62
4.3 Diodes for Solid State Laser Pumping 64
4.4 The POLARIS Laser 66
4.5 The Five Ampli.cation Stages of POLARIS 68
4.6 The Tiled Grating Compressor 73
4.7 Future Prospects 76
References 76
5 The Megajoule Laser – A High-Energy-Density Physics Facility 79
5.1 LMJ Description and Characteristics 79
5.2 LIL Performances 82
5.3 LMJ Facility 85
5.4 LMJ Ignition and HEDP Programs 87
5.5 Conclusions 88
Acknowledgment 89
References 89
Part II Sources 90
6 Electron and Proton Beams Produced by Ultrashort Laser Pulses 91
6.1 Introduction 91
6.2 Theoretical Background 92
6.3 Results in Electron Beam Produced by Nonlinear Plasma Waves 94
6.4 Proton Beam Generation with Solid Targets 96
6.5 Perspectives 97
6.6 Conclusion 99
Acknowledgments 99
References 99
7 Laser-Driven Ion Acceleration and Nuclear Activation 101
7.1 Introduction 101
7.2 Basic Physical Concepts in Laser – Plasma Ion Acceleration 102
7.3 Typical Experimental Arrangement 104
7.4 Recent Experimental Results 107
7.5 Applications to Nuclear and Accelerator Physics 112
7.6 Conclusions and Future Prospects 114
Acknowledgments 115
References 116
8 Pulsed Neutron Sources with Tabletop Laser- Accelerated Protons 118
8.1 Introduction 118
8.2 Recent Proton Acceleration Experiments 119
8.3 Neutron Production with Laser-Accelerated Protons 122
8.4 Laser as a Neutron Source? 129
8.5 Optimization of Neutron Source – Nuclear Applications with Future Laser Systems? 131
8.6 Conclusions 135
References 136
Part III Transmutation 138
9 Laser Transmutation of Nuclear Materials* 139
9.1 Introduction 139
9.2 How Constant Is the Decay Constant? 141
9.3 Laser Transmutation 142
9.4 Conclusions 153
References 153
10 High-brightness y- Ray Generation for Nuclear Transmutation 155
10.1 Introduction 155
10.2 Principles of this Scheme 156
10.3 Transmutation Experiment on New SUBARU 163
10.4 Transmutation System 168
10.5 Conclusions 174
References 174
11 Potential Role of Lasers for Sustainable Fission Energy Production and Transmutation of Nuclear Waste 176
11.1 Introduction 176
11.2 Economics of Nuclear Power Initiatives 179
11.3 Technology Features for New Initiatives 180
11.4 The Sealed Continuous Flow Reactor 181
11.5 Laser-Induced Nuclear Reactions 185
11.6 Introducing Fusion Neutrons into Waste Transmutation 185
11.7 Comparison of the Fission and d – t Fusion Energy Resources 189
11.8 Implications for Fusion Energy Research 190
11.9 Summary and Conclusions – Implications for Nuclear Power R& D
References 193
11.10 Appendix 194
12 High-Power Laser Production of PET Isotopes 197
12.1 Introduction 197
12.2 Positron Emission Tomography 198
12.3 Proton Acceleration with a High-Intensity Laser 200
12.4 Experimental Setup 201
12.5 Experimental Results 205
12.6 Future Developments and Conclusions 208
Acknowledgments 208
References 209
Part IV Nuclear Science 210
13 Nuclear Physics with High-Intensity Lasers 211
13.1 Introduction 211
13.2 Search for NEET in 211
13.3 Excitation of an Isomeric State in 216
13.4 E.ect of High Fields on Nuclear Level Properties 218
13.5 Conclusions 219
References 220
14 Nuclear Physics with Laser Compton y-Rays 221
14.1 Introduction 221
14.2 Laser Compton Scattering 222
Rays 222
14.3 Nuclear Physics and Nuclear Astrophysics 224
14.4 Nuclear Transmutation 230
14.5 Conclusion 231
Acknowledgment 231
References 231
15 Status of Neutron Imaging 234
15.1 Introduction 234
15.2 The Setup of Neutron Imaging Facilities 237
15.3 Modern Neutron Imaging Detectors 241
15.4 Improved Neutron Imaging Methods 244
15.5 The Application of Neutron Imaging 249
15.6 Future Trends and Visions 251
15.7 Conclusions 251
References 251
Index 253

3 Laser-Triggered Nuclear Reactions (p. 25-26)

F. Ewald
Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena
Max-Wien-Platz 1, 07743 Jena

3.1 Introduction

Nearly 30 ago, laser physicists dreamed of the laser as a particle accelerator [1]. With the acceleration of electrons, protons, and ions up to energies of several tens of MeV by the interaction of an intense laser pulse with matter, this dream has become reality within the last ten years. Today, highly intense laser systems drive microscopic accelerators. Nuclear reactions are induced by the accelerated particles. This article intends to outline the unique properties of laser-based particle and bremsstrahlung sources, and the diversity of new ideas that arise from the combination of lasers and nuclear physics.

Triggering nuclear reactions by a laser is done indirectly by accelerating electrons to relativistic velocities during the interaction of a very intense laser pulse with a laser-generated plasma. These electrons give rise to the generation of energetic bremsstrahlung, when they are stopped in a target of high atomic number. They can as well be used to accelerate protons or heavier ions to several tens of MeV. Those bremsstrahlung photons, protons, and ions with energies in the typical range of the nuclear giant dipole resonances of about a few to several tens of MeV may then induce nuclear reactions, such as fission, the emission of photoneutrons, or proton-induced emission of nucleons. To induce one of these reactions, a certain energy threshold – the activation energy of the reaction – must be exceeded.

Since the .rst demonstration experiments, nuclear reactions were used for the spectral characterization of laser-accelerated electrons and protons as well as bremsstrahlung [2, 3, 4, 5]. A whole series of classical known nuclear reactions has been shown to be feasible with lasers, such as photo-induced .ssion [6, 7], proton- and ion-induced reactions [5, 8, 9], or deuterium fusion [10, 11, 12, 13, 14]. Recently the cross section of the (ã,n)-reaction of 129I was measured in laser-based experiments [15, 16, 17].

This last step from the pure observation of nuclear reactions to the measurement of nuclear parameters is of importance regarding the small size of nowaday’s high-intensity laser systems compared to large accelerator facilities. It is a .rst step to a possible joint future of nuclear and laser physics. Nevertheless, all probable future applications of laser-induced nuclear reactions would need to have properties that are not covered by classical nuclear physics. Otherwise, they would stay a diagnostics tool for laser–plasma physicists. The striking properties of a laser as driving device for nuclear reactions are its small tabletop size, the possibility to switch very fast from one accelerated particle to another as well as the ultrashort duration of these particle and bremsstrahlung pulses.

3.2 Laser–Matter Interaction

The basis of all laser-triggered nuclear reactions is the acceleration of particles such as electrons, protons, and ions as well as the generation of high-energy bremsstrahlung photons by the interaction of very intense laser pulses incident on matter. The mechanisms of particle acceleration change sensitively with the target material and chemical phase. The choice of target material in conjunction with the laser parameters is important for the control of plasma conditions and therewith for the control of optimum particle acceleration.

Gaseous targets and underdense plasmas are suited best for the acceleration of electrons to energies of several tens of MeV [18, 19, 20, 21]. Thin solid targets, in contrary, are used to accelerate protons and ions [5, 22, 23, 24]. Deuterium fusion reactions have been realized with both heavy water droplets and deuterium-doped plastic [10, 12, 14]. Therefore, but without being exhaustive, the different acceleration mechanisms of electrons, protons, and ions that are important for the production of energetic electrons, protons, and photons are outlined in this section.